It has become evident that asphaltenes and resins, asphaltic acids, as well as clay and other minerals are the principal stabilizers of crude petroleum emulsions. It is assumed by applicant that highly polar asphaltene and resin fractions relatively enriched in heteroatoms (oxygen, nitrogen, and sulfur) form films at the water-oil interfaces which stabilize the emulsions. In situ water in oil (W/O) emulsions produced from high viscosity oils are difficult to break and may require different demulsification chemical formulations over the lifetime of the well. Crudes obtained by secondary recovery methods from conventional crude wells also form permanent emulsions which are difficult to break. Tar sands and oil shales processing can produce stable emulsions of this type, as can various heavy oil recovery projects.
Diluting heavy oil emulsions with light solvents, e.g. toluene, naphtha, cyclohexane, decane, etc., reduces the specific gravity of the oil phase and lowers the viscosity. This permits separation of part of the water. However, even with equal amounts of hydrocarbon solvent and emulsion, and with prolonged settling periods, the water content remains above the acceptable limit of one percent for subsequent refinery processing. The last several percent water is usually the most difficult to remove from the system.
Many additives have been used with some effect in breaking water-in-oil emulsions. For example, oleic acid (U.S. Pat. No. 1,500,202) and natural oils such as whale oil, palm oil etc. (U.S. Pat. No. 2,290,411) have been used as demulsifiers. A reaction product of blown tall oil, an alkylolamine, a metal salt etc. has been used (U.S. Pat. Nos. 2,568,741-743) The use of methylethyl ketone has been mentioned in U.S. Pat. No. 2,324,492. Complex reaction products of phenol-aldehyde or alkylphenol-ethylene oxide components are described as demulsifiers (U.S. Pat. No. 2,571,119 and U.S. Pat. No. 3,553,149). The art seems to be moving toward tailoring synthetic reaction products for specific applications as demulsifiers. While many of these reaction product demulsifiers are effective in low concentrations, in most cases they are found to be expensive, non-recoverable or impractical to recover.
It would be desirable to find some effective demulsifiers which are not of high cost and are also recoverable and suitable for recycle.